Composite materials produced by bonding a sheet-like material such as polyvinyl chloride sheet or leather as a skin on a base material such as hard board or fiber board by high-frequency welding via a core, which has been obtained by impregnating a soft foam such as urethane foam, a non-woven fabric of a synthetic resin or the like with a vinylidene chloride-based copolymer latex and then drying them, have conventionally been used as vehicle-interior finish materials, for example, as automobile door trims, ceiling and the like (Japanese Patent Publication No. 41910/1976; Japanese Utility Model Publication No. 40526/1986).
In recent years, there is however an ever-increasing market demand for automobile parts, components and the like of still higher quality with a view toward making further improvements in various performance and durability. Of these, vehicle-interior finish materials are required to meet an especially stringent standard for heat resistance so that the bonding between each adjacent layers should be strong and heat-resistant. An accelerated testing method which is more severe than the conditions of a conventional evaluation test has already been introduced. Reflecting these requirements, there is an outstanding demand for further improvements in both materials to be used and performance. The conventional composite vehicle-interior finish materials are however still insufficient in heat resistance, adhesive strength and the like in view of the quality standard required in the market.